1) Field of the Invention
The present invention relates to an ignition device for use in an internal combustion engine, which has an integral construction of an ignition plug and an ignition coil.
2) Description of the Related Art
So far, as ignition devices for use in internal combustion engines, there have been proposed various types (see Japanese Patent Laid-Open Nos. 2000-252040 and 2000-277232 and European Patent Laid-Open No. 0907019). In such types of ignition devices, each of primary and secondary windings is wound around a resin-made spool and a connector terminal, to which connected is an end portion (terminal) of the winding, is insert-molded in a resin-made spool.
Meanwhile, the present inventors have studied the replacement of one of the two spools with a ceramic spool and an integral construction of a plug side tube section, internally including a center electrode and a stem, and the ceramic spool for the purpose of the cost reduction based on the structural simplification. However, this has indicated the following problems.
That is, in the case of a conventional resin-made spool, a connector terminal is insert-molded in the spool to inhibit motions of the connector terminal with respect to the spool, which can facilitate the terminal connection work for the connection between an end portion of a winding and the connector terminal.
However, for a spool to be of a ceramics-made type, difficulty is experienced in insert-molding a connector terminal in a spool, which leads to arbitrary motions of the connector terminal with respect to the spool during the terminal connection work, thereby creating a problem in the impairment of workability of terminal connection.
The present invention has been developed with a view to eliminating the above-mentioned problem, and it is therefore an object of the invention to eliminate problems occurring in the case of the employment of a ceramic spool in an ignition device for an internal combustion engine in which a spark plug and an ignition coil are integrated with each other and is mounted in a cylinder head.
For this purpose, in accordance with the present invention, there is provided an ignition device for an internal combustion engine, which is equipped with a spark plug (2) made to carry out an electric discharge between an center electrode (22) and an earth electrode (23) and an ignition coil (3) having a primary winding (31) and a secondary winding (32) for supplying a high voltage to the spark plug (2), with the spark plug (2) and the ignition coil (3) being mounted in a cylinder head of the internal combustion engine in an integrated condition, the ignition device comprising a tube-like ceramic spool (52) on which one of the primary winding (31) and the secondary winding (32) is wound, two conductive connector terminals (61) located at an axial end portion of the spool (52) and connected to both end portions (31a) of the winding (31) wound on the spool (52), an insulating-resin-made holding member (9) into which the two connector terminals (61) are incorporated, and positioning means (55, 92) for inhibiting a relative motion of the connector terminals (61) and the holding member (9) with respect to the spool (52) in circumferential directions of the spool (52).
This inhibits the motion or movement of the connector terminals with respect to the ceramic spool in the circumferential directions of the spool during the terminal connection work for establishing the connection between the windings and the connector terminals, thus improving the workability or work efficiency of the terminal connections.
In addition, according to the present invention, it is also appropriate that the positioning means (55, 92) comprises a notch portion made in the spool (52) and a projecting portion (92) made in the holding member (9) to engage with the notch portion (55). This contributes to the facilitation of the construction of the ignition device according to the present invention.
Still additionally, according to the present invention, it is also appropriate that the spool (52) is integrated with a ceramics-made plug side tube section (51) internally accommodating the center electrode (22). This contributes to the facilitation of the construction of the ignition device according to the present invention, thereby achieving the cost reduction.
The reference numerals in parentheses attached to the respective means or members signify the corresponding relation with respect to the concrete means in an embodiment which will be described later.